1. Field of the Invention
This invention relates to a process cartridge and an electrophotographic apparatus which have a charging means and an electrophotographic photosensitive member. More particularly, it relates to a process cartridge and an electrophotographic apparatus which have a specific charging member and an electrophotographic photosensitive member having a surface layer containing a specific resin and fluorine-containing resin particles.
2. Related Background Art
In recent years, electrophotographic photosensitive members having various organic photoconductive compounds have been widely investigated. For example, U.S. Pat. No. 3,837,851, discloses a photosensitive member having a charge transport layer containing triarylpyrazoline, and U.S. Pat. No. 3,871,880 discloses a photosensitive member comprising a charge generation layer and a charge transport layer, the former containing a derivative of a perylene pigment and the latter being formed of a condensation product of 3-propylene with formaldehyde.
The organic photoconductive compounds have their own different wavelength regions where they are sensitive. For example, Japanese Patent Applications Laid-open No. 61-272754 and No. 56-167759 disclose compounds having a high sensitivity at the visible region, and Japanese Patent Applications Laid-open No. 57-19567 and No. 61-228453 disclose compounds having a sensitivity at the infrared region. Of these compounds, those having a sensitivity at the infrared region are used in laser beam printers (hereinafter xe2x80x9cLBPxe2x80x9d) and LED printers, and the demand for them and their use are increasing.
As for the charging means, Japanese Patent Applications Laid-open No. 57-17826 and No. 58-40566 disclose a contact charging means which charges an electrophotographic photosensitive member electrostatically by applying a voltage to a charging member provided in contact with the electrophotographic photosensitive member.
The contact charging means has advantages that it may cause ozone in a much smaller quantity than corona charging means, and the contact charging means is very economical because it does not waste electric currents. The corona charging means may waste by about 80% of electric currents which flow to a shield among those flowing to a charging assembly.
However, since in the contact charging means the contact charging member comes into contact with the electrophotographic photosensitive member, the electrophotographic photosensitive member is required to have a superior mechanical strength. For the purpose of improving charging stability, it is also proposed to use as applied voltage a voltage formed by superimposing an AC voltage on a DC voltage (Japanese Patent Application Laid-open No. 63-149668). In this method, although the charging stability is improved, electric currents flow to the electrophotographic photosensitive member in a very large quantity. As a result, the scrape (amount of scrape) of the electrophotographic photosensitive member may increase to cause fog on images, bringing about an additional problem. Thus, studies were conducted to provide a means by which not only mechanical strength but also electrical strength can be improved.
However, when a surface layer of the electrophotographic photosensitive member is scraped less because of an improvement of mechanical and running performance, or when, even though more scraped to a certain extent, the surface layer has a large surface roughness, a resin having been deteriorated by oxidation and surface deposits can not completely be removed to cause a reduction of resistance on the photosensitive member surface, to cause a phenomenon where images formed are smeared and become smeared (hereinafter xe2x80x9csmeared imagesxe2x80x9d). Also, when the surface layer has a large surface roughness, the light-area potential may increase to cause a decrease in image density.
This phenomenon may particularly occur when a contact charging means is used which employs a voltage formed by superimposing an AC voltage on a DC voltage, and may further substantially occur when fully moistened paper is used as a transfer medium.
As a means for preventing the smeared images, Japanese Patent Application Laid-open No. 62-160458 discloses using both a low-molecular weight polycarbonate resin and a high-molecular weight polycarbonate resin so that a deteriorated surface layer of the electrophotographic photosensitive member can be removed together with deposits. Such a means, however, can not be very effective because the electrophotographic photosensitive member may exhibit a larger surface roughness with use when the above specific contact charging means is employed.
An object of the present invention is to provide a process cartridge and an electrophotographic apparatus which have an electrophotographic photosensitive member having a superior running performance and also hardly causing smeared images and an increase in light-area potential.
The present invention provides a process cartridge comprising;
an electrophotographic photosensitive member comprising an electroconductive support and a photosensitive layer provided on the support; and
a charging means having a charging member which is provided in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member electrostatically by applying a voltage formed by superimposing an alternating-current voltage on a direct-current voltage;
the electrophotographic photosensitive member and the charging means being supported as one unit and being detachably mountable to the main body of an electrophotographic apparatus; and
the electrophotographic photosensitive member having a surface layer which contains i) at least one of a polyarylate resin having a weight-average molecular weight of from 7.5xc3x97103 to 3.7xc3x97104 and having a structural unit represented by the following Formula (1) and a polycarbonate resin having a weight-average molecular weight of from 7.5xc3x97103 to 3.7xc3x97104 and having a structural unit represented by the following Formula (2), and ii) fluorine-containing resin particles 
xe2x80x83wherein X1 represents xe2x80x94CR13R14xe2x80x94 (where R13 and R14 are the same or different and each represent a hydrogen atom, a trifluoromethyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group), a substituted or unsubstituted cycloalkylidene group, a substituted or unsubstituted xcex1,xcfx89-alkylene group, a single bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94SO2xe2x80x94; and R1 to R12 are the same or different and each represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group; 
wherein X2 represents xe2x80x94CR23R24xe2x80x94 (where R23 and R24 are the same or different and each represent a hydrogen atom, a trifluoromethyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group), a substituted or unsubstituted cycloalkylidene group, a substituted or unsubstituted xcex1,xcfx89-alkylene group, a single bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94SO2xe2x80x94; and R15 to R22 are the same or different and each represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group.
The present invention also provides an electrophotographic apparatus comprising;
an electrophotographic photosensitive member comprising an electroconductive support and a photosensitive layer provided on the support;
a charging means having a charging member which is provided in contact with the electrophotographic photosensitive member and charges an electrophotographic photosensitive member electrostatically by applying a voltage formed by superimposing an alternating-current voltage on a direct-current voltage;
an exposure means for exposing to light the electrophotographic photosensitive member charged, to form an electrostatic latent image;
a developing means for developing the electrostatic latent image by the use of a toner, to form a toner image; and
transferring to a transfer medium the toner image formed;
the electrophotographic photosensitive member having a surface layer which contains i) at least one of a polyarylate resin having a weight-average molecular weight of from 7.5xc3x97103 to 3.7xc3x97104 and having a structural unit represented by the following Formula (1) and a polycarbonate resin having a weight-average molecular weight of from 7.5xc3x97103 to 3.7xc3x97104 and having a structural unit represented by the following Formula (2), and ii) fluorine-containing resin particles 
xe2x80x83wherein X1 represents xe2x80x94CR13R14xe2x80x94 (where R13 and R14 are the same or different and each represent a hydrogen atom, a trifluoromethyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group), a substituted or unsubstituted cycloalkylidene group, a substituted or unsubstituted xcex1,xcfx89-alkylene group, a single bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94SO2xe2x80x94; and R1 to R12 are the same or different and each represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group; 
wherein X2 represents xe2x80x94CR23R24xe2x80x94 (where R23 and R24 are the same or different and each represent a hydrogen atom, a trifluoromethyl group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group), a substituted or unsubstituted cycloalkylidene group, a substituted or unsubstituted xcex1,xcfx89-alkylene group, a single bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94SO2xe2x80x94; and R15 to R22 are the same or different and each represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group.